That scribble looks like a date! It's probably not worth a fortune - I'm inheriting a solid gold 1915 Lange & Sohne PW that is worth around $10,000 so being Waltham you might find this is worth perhaps half that or less - but certainly worth getting valued and serviced for sure. What would be nice is if you could pop the back open and take a pic of the movt. I suspect you will find that it is beautifully decorated - something US PW makers were very good at - in fact they could knock spots off the swiss in movt decoration.